fruits of an unlawful detention. A woman had been raped in her home, and during the next 10 days, the local police rounded up scores of black youths, randomly stopping, interrogating, and fingerprinting them. Davis’ prints were discovered to match a set found at the scene of the crime, and on that basis he was arrested and convicted. Had it not been for Davis’ illegal detention, however, his prints would not have been obtained and he would never have become a suspect.' Here, in contrast, the robbery investigation had already focused on respondent, and the police had independent reasonable grounds to suspect his culpability.
We find Bynum v. United States, 104 U. S. App. D. C. 368, 262 F. 2d 465 (1958), cited with approval in Davis, supra, at 724, helpful in our analysis as well. In Bynum, the defendant voluntarily came down to the police station to look for his brother, who had been arrested earlier that day while driving an auto sought in connection with a robbery. After telling one of the officers that he owned the car, Bynum was arrested and fingerprinted. Those prints were later found to match a set at the scene of the robbery, and Bynum was convicted based in part on that evidence. The Court of Appeals held that the police lacked probable cause at the time of Bynum’s arrest, and it ordered the prints suppressed as “something of evidentiary value which the public authorities have caused an arrested person to yield to them during illegal detention.” 104 U. S. App. D. C., at 370, 262 F. 2d, at 467. As this Court noted in Davis, however, 394 U. S., at 725-726, n. 4, Bynum was subsequently reindicted for the same offense, and the Government on retrial introduced an older set of his fingerprints, taken from an FBI file, that were in no' way connected with his unlawful arrest. The Court of Appeals affirmed that conviction, holding that the fingerprint identification made on the basis of information already in the FBI’s possession was not tainted by the subsequent illegality and was therefore admissible. Bynum v. United States, 107 U. S. App. D. C. 109, 274 F. 2d 767 (1960).